April 13, 2021
In the future, only "water that meets the regulatory standards for discharge into the environment regarding nuclides other than tritium" will be termed "ALPS treated water."
At TEPCO's FDNPS, contaminated water is generated from both groundwater and rainwater coming into contact with radioactive materials in the building, as well as from stagnant water in the building after it has been used to cool the fuel debris (melted fuel).
The water has been processed using ALPS and other processes to remove most radionuclides, apart from tritium, and then stored in tanks as “ALPS treated water.” However, as the number of storage tanks has increased and they have taken up more and more space on the FDNPS premises, handling of the water in tanks has become an issue.
Given this setting, at the Ministerial Conference of Contaminated Water, Treated Water and Decommissioning issues held on April 13, the Basic Policy was made to address the issue by releasing the ALPS treated water into the ocean approximately two years later.
2. Changes to the definition of ALPS treated water
Approximately 70% of the water currently stored in the tanks contains radioactive substances other than tritium, as well as tritium at concentrations that exceed the regulatory standards. The reasons for this include factors such as past malfunctions in the purification systems, and the use of purification processes that prioritized maximizing the quantity treated in order to quickly reduce the impact of untreated contaminated water (direct radiation) on the surrounding areas.
The Basic Policy decided on April 13 states that when discharging of ALPS treated water, safety is to be ensured by re-purifying and diluting the treated water to make sure that the concentrations of tritium and other radioactive substances are significantly below the regulatory standards. However, the situation as outlined above has led some people to mistakenly understand that the water released into the environment will be contaminated, or contain higher concentrations of radioactive materials than allowed by the regulatory standards.
In order to prevent reputational damage based on such misunderstandings, in the future, only "water that meets the regulatory standards for discharge into the environment regarding nuclides other than tritium" will be termed "ALPS treated water."
Division in Charge
Nuclear Accident Response Office, Agency for Natural Resources and Energy